The matter of this application corresponds to the matter contained in Disclosure Document 454147 filed Apr. 1, 1999, wherein this application assumes the priority date of that document.
1. Field of the Invention
In general, the present invention relates to hydrogen diffusion cells. More particularly, the present invention relates to hydrogen diffusion cells that contain wound coils of palladium tubing.
2. Description of the Prior Art
In industry, there are many known techniques for separating hydrogen from more complex molecules in order to produce a supply of hydrogen gas. One such technique is electrolysis, wherein hydrogen gas is obtained from water. Regardless of how hydrogen gas is obtained, the collected hydrogen gas is typically contaminated with secondary gases, such as water vapor, hydrocarbons and the like. The type of contaminants in the collected hydrogen gas are dependent upon the technique used to generate the hydrogen gas.
Although contaminated hydrogen gas is useful for certain applications, many other applications require the use of pure hydrogen. As such, the contaminated hydrogen gas must be purified. One technique used to purify hydrogen is to pass the hydrogen through a hydrogen diffusion cell. A typical hydrogen diffusion cell contains a single coil of palladium tubing. The palladium tubing is heated and the contaminated hydrogen gas is directed through the palladium tubing. When heated, the palladium tubing is permeable to hydrogen gas but not to the contaminants that may be mixed with the hydrogen gas. As such, nearly pure hydrogen passes through the palladium tubing and is collected for use.
Prior art hydrogen diffusion cells that use a coil of palladium tubing have many problems. One of the major problems is that of reliability. As a coil of palladium tubing is repeatedly heated and cooled, it expands and contracts. The longer the wound tube is, the more the tube expands and contracts. As the palladium tubing expands and contacts, cracks occur in the tubing. Cracks are particularly prevalent at the ends of the tubing where the palladium tubing is welded to common piping. Once a crack occurs in the palladium tubing or the welded supports of the tubing, the hydrogen diffusion cell ceases to function properly.
One solution that has been attempted to increase the reliability of hydrogen diffusion cells is to decrease the length of the palladium tubing and/or the number of windings in the coil of palladium tubing. These techniques reduce the degree of expansion and contraction experienced by the palladium tubing but also greatly decrease the surface area of the palladium tubing and thus the output and efficiency of the hydrogen diffusion cell.
A need therefore exists for a new hydrogen diffusion cell that has increased reliability yet does not have decreased flow efficiency. This need is met by the present invention as it is described and claimed below.
The present invention is a hydrogen diffusion cell that is used to purify contaminated hydrogen gas. The hydrogen diffusion cell has a supply tube that supplies contaminated hydrogen gas and a drain tube that removes contaminated hydrogen gas. Hydrogen permeable coils are disposed between the supply tube and the drain tube. The coils include at least one small diameter coil. Concentrically surrounding the small diameter coil is at least one larger diameter coil. All coils are mounted in such a manner that they maintain a constant radius of curvature along their entire lengths.
As contaminated hydrogen passes from the supply tube to the drain tube through the various coils, purified hydrogen permeates through the material of the coils and is collected from a confined space that surrounds the coils.